Police in Houston, Texas responded to reports of an active shooter at Ben Taub Hospital. The hospital was placed on lockdown, and some patients were evacuated. No suspect or evidence of the shooting have been found, HPD Chief Art Acevedo told reporters.

Officers are searching the hospital, but have not found any victims so far, the Houston Police Department said.

“We have not found the suspect, and we have not found evidence of an active shooter,” Chief Art Acevedo told reporters at 3:15pm local time.

Several witnesses have described the suspect as a bald white male of unknown age, Acevedo said, but the police have not found any trace of him, or evidence of the shooting.

About an hour before the first reports of shots fired, St. Mark’s Episcopal School in Bellaire tweeted a picture of fifth grade students holding up paintings and posing with hospital staff. The school would not answer whether the students were still at the hospital, the Houston Chronicle reported.